From owner-freebsd-current Fri Apr 5 02:56:05 1996 Return-Path: owner-current Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id CAA11103 for current-outgoing; Fri, 5 Apr 1996 02:56:05 -0800 (PST) Received: from originat.demon.co.uk (originat.demon.co.uk [158.152.220.9]) by freefall.freebsd.org (8.7.3/8.7.3) with ESMTP id CAA11098 for ; Fri, 5 Apr 1996 02:56:01 -0800 (PST) Received: (from paul@localhost) by originat.demon.co.uk (8.7.5/8.6.9) id MAA00692; Fri, 5 Apr 1996 12:56:29 +0100 (BST) From: Paul Richards Message-Id: <199604051156.MAA00692@originat.demon.co.uk> Subject: Re: fast memory copy for large data sizes To: davidg@Root.COM Date: Fri, 5 Apr 1996 12:56:29 +0100 (BST) Cc: asami@cs.berkeley.edu, current@FreeBSD.org, nisha@cs.berkeley.edu, tege@matematik.su.se, hasty@rah.star-gate.com In-Reply-To: <199604051021.CAA00222@Root.COM> from "David Greenman" at Apr 5, 96 02:21:48 am Reply-to: paul@netcraft.co.uk X-Mailer: ELM [version 2.4 PL23] MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-current@FreeBSD.org X-Loop: FreeBSD.org Precedence: bulk In reply to David Greenman who said > > size libc ours > > 32 15.258789 MB/s 6.103516 MB/s > > 64 20.345052 MB/s 15.258789 MB/s > > 128 17.438616 MB/s 15.258789 MB/s > > This would be a big lose in the kernel since just about all bcopy's fall > into this range _except_ disk I/O block copies. I know this can be done better > using other techniques (non-FP, see hackers mail from about 3 months ago). You > should talk to John Dyson who's also working on this. A quick check of the size would probably help and use the original method for small copies. Run a benchmark on such a scheme and see what happens. Anyway, I had another thought, do we save the fp registers across context switches? I seem to remember that we don't always and instead save them when something tries to do FP operations, I might be imagining this but if it's true increased use of the fp regs is going to impact context switching. -- Paul Richards, Originative Solutions Ltd. Internet: paul@netcraft.co.uk, http://www.netcraft.co.uk Phone: 0370 462071 (Mobile), +44 1225 447500 (work)